## 1.18. The Superuser (Root)

In general, a process (Section 24.1) is a program that's running: a shell, the ls command, the vi editor, and so on. In order to kill a process (Section 24.12), change its priority (Section 26.5), or manipulate it in any other way, you have to be the process' owner (i.e., the user who started it). In order to delete a job from a print queue (Section 45.1), you must be the user who started it.

As you might guess, there needs to be a way to circumvent all of this security. Someone has to be able to kill runaway programs, modify the system's files, and so on. Under Unix, a special user known as root (and commonly called the "superuser") is allowed to do anything.

To become the superuser, you can either log in as root or use the su (Section 49.9) command. In this book, though, we'll assume that you don't have the superuser password. Almost all of what we describe can be done without becoming superuser.

-- ML

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